Many types of power-operated hand tools such as saber saws or jig saws are available. Many of these bayonet-type saws are capable of producing an orbital blade motion. Such a motion has a rectilinear component of a generally up and down nature, and a fore and aft motion advancing the cutting blade into the workpiece. Typically the blade advances on the cutting stroke, which conventionally is the upstroke on most saws.
One of the principal advantages of the bayonet type saw over circular saws and hand-operated band-type saws is the ability of the bayonet saw to make a curved cut along a relatively short radius.
Some bayonet-type saws have orbital motions which can be varied by the operator. Typically, when performing tight scrolling cuts, a rectilinear blade motion has been required. Performing small radius cuts exerts a twisting action on the cutting blade which can make control of the cutting path difficult. In many cases, this lack of control has resulted from the blade guide portion of the bayonet saw being incapable of adequately supporting and guiding the cutting blade.
Heretofore, bayonet-type saws have typically included a blade guide which has a roller wheel mounted for rotation along an axis generally parallel to the work surface and perpendicular to the up and down rectilinear blade motion. Such a blade guide supports only the back side of the cutting blade. During scroll cutting, the lack of lateral support of the cutting blade has proven disadvantageous.
A modified version of the above-described blade guide includes a notched or grooved roller bearing supporting the cutting blade. Such a bearing has a blade receiving groove or slot within the blade engaging surface. The blade rests in the slot and therefore is supported along its back side, and along the rear most portion of the sides of the blade, for the depth of the groove or slot. A grooved blade guide roller will typically prevent the back portion of the blade from moving laterally across the roller surface, but is of limited assistance in stabilizing the blade against twisting action encountered during scroll cutting. Attempting to make tight radial cuts with even this type of device can lead to a lack of control. The addition of an orbital motion to the blade, which normally speeds cutting of soft material such as wood, further aggravates the problem.
Consequently, currently available bayonet-type saws have required that scroll cutting be performed at an operating speed below the operator's ability because of the physical limitations of the tool.
The present invention provides an improved bayonet-type saw having a variable orbital blade motion. The saw includes a blade guide having a main rotating bearing, for engaging the back side of a cutting blade, and a pair of nip roller bearings for engaging the sides of the cutting blade. The saw also provides electronic speed control of the blade motion, and further includes a structure for selectively blowing air toward the cutting region for removing debris and saw dust to improve operator visibility of the cutting blade. Improved operator control and productivity are achieved. Scroll cutting, even with moderate orbital motion, and increased speed are possible.